The left atrial phasic functions and the relationship with plasma N-terminal pro-B-type natriuretic peptide levels and symptomatic states in patients with hypertrophic cardiomyopathy.

OBJECTIVE: We aimed to evaluate left atrium (LA) phasic functions and relation with N-terminal pro-B- type natriuretic peptide (NT-proBNP) levels and symptomatic states of the patients with hypertrophic cardiomyopathy (HCM).

METHODS: Left atrial volume was calculated at end-systole (Vmax), end-diastole and pre-atrial contraction by echocardiography in 75 patients with HCM and 75 control subjects. Left atrial ejection fraction (LAEF), expansion index (LAEI), active emptying volume index (LAAEVI) and fraction (LAAEFr), passive emptying volume index (LAPEVI) and fraction (LAPEFr) were calculated. NT-proBNP levels were measured.

RESULTS: Left atrial active emptying volume (LAAEV) positively correlated with Vmax (r=0.343, p=0.003) up to a point, but then reached a plateau with larger LA volumes in HCM group. The LAAEFr was the only variable which was similiar between asymptomatic patients and controls, but was significantly decreased in symptomatic patients (p<0.05). NT-proBNP was correlated with LAEF (r=-0.32, p=0.005), LAEI (r=-0387, p=0.001), and LAAEFr (r=-0.25, p=0.035) but not related with LAPEFr (p=0.4). In receiver operating characteristic curve analysis an NT-proBNP cut-off value of 1415 pg/mL identified reduced LAEF with 87% specificity and 59% sensitivity [AUC=0.77 (95% CI: 0.65-0.89), p=0.004], a cut-off value of 820 pg/mL predicted impaired LAEI with 81% specificity ve 67% sensitivity [AUC=0.78 (95% CI: 0.66-0.9), p<0.001]; while a cut-off value of 1320 pg/mL predicted impaired LAAEFr with 76% specificity and 67% sensitivity [AUC=0.79 (95% CI: 0.68-0.91), p=0.02].

CONCLUSION: In HCM, LA phasic functions alter according to the Frank-Starling mechanism indicating occurrence of a secondary atrial myopathy. Impairment of LA booster pump function seems to be associated with appearance of symptoms and NT-proBNP levels predict the deterioration of LA reservoir and pump functions in HCM population.